Trigger switch



Dec. 31, 1929. w STUMPF 1,741,383

TRIGGER SWITCH Filed March ze. 1926 2 sneets-shee 1 W. STUMPF 4 TRIGGER SWITCH Gee. 31, 1929.

Filed March 26, 1926 2 Sheets-Sheet Patented Dec. 31, 1929 UNITED sTATEs'PATNr oFFlcE WALTER STUMPF, OF BALTIMORE COUNTY, MARYLAND, ASSIGNQR. T0 THE BLACK & BECKER MANUFACTURING COMPANY, OF TOWSON, MARYLAND, A CORPORATION OF MARYLAND TRIGGER SWITCH Application filed March 26, .1926. Serial No. 97,601.

The invention relates to portable electric tools, as drills, tapprs, valve grinders and the like, which are of more or less similar construction, and particularly to the circuit breaking means or switch by which the motor and the operation of the tool are started, stopped and Controlled.

The switch is preferably of the trigger actuated type, which is regarded as the quickest, most convenient and depen'dable for the purpose in hand.' It comprises a contaet block which is rotated intermittently by means of a ratchet secured to the contact block or to the shaft on which it is mounted and a pawl carried by the trigger.

' The contact block in the preferred form, as illustrated, is of cylindrical or substantially cylindrical form. This block as it rotates presents alternately to the switch Mades in contact with its surface, an'area of insulating and an area of conducting material. The conducting and non-eonducting areas may be divided into any convenient number of units, the conducting areas being spaced apart in the direction of rotation by intervening areas of non-conducting or insulating material.

The switch blades are in the form of plate Springs bearing at their ends on the contact block with a slight degree of pressure produced by spacing the ends of the springs in their normal or unfiexed position by a distance less than the diameter of the contact blocks, causing flexing of the blades when the contact block is inserted between them.

To give a quickmaking and breaking of the contact or the snapping action of the switch, which is considered desirable as contributing to quick operation and preventing burning of the contacting members by arcing, a star wheel or similar device is mounted on the shaft of the contact block and this is engaged by a spring pressed follower or wiper, the points of the star being so spaced as to pass the follower at the time of making and breaking the -circuit, the action of the follower as it passes the pointof the star imparts to the latter a quick snap which is converted into a quick rotation of'the contactv member at the exact instants of making and breaking the contact.

In the accompanying drawing I have illustrated a switch e'mbodying the features of my invention in the preferred form and so much of an electric tool as is considered helpful to a full comprehension of the application of the switch.

In the drawing:

F igure 1 is a plan of the switch and casing removed. p

Figure 2 is a 'section on the line 2-2 of Figure 1.

Figure 3 is a detailed View in the nature of an elevation in a ane at right angles to the axis of the switcli, showing the star wheel and follower or snapper.

F igure 4 is an elevation of an electric tool equipped with theswitch of the invention.

F igure 5 is a section on the line 5-5 of Figure 1, showing the contact block on an enlarged scale.

Referring to the drawings by numerals, each of which is used to indicate the same or 'similar parts in the different figures, the

switch as shown comprises a rotary contact member 1 mounted on a shaft 2, which is preferably square to provide for the angular positioning of the rotary partsv relatively thereto, switch' blades 3, 4, 5, 6 and blade block 7, star wheel 8, snapper 9 and ratchet and pawl 10 and 11.

The contact member 1 is preferably secured to a tubular hub 13 having a square axial opening` to fit shaft 2 and is made `of any suitable insulating material, as bone fiber or the like. The contact block and other parts on the hub or tube 13 are held in position by a nut 12 at one end and flange 19 at the other end of the tube or hub, and it is provided on its surface with one or more notches or grooves 14 in the surface parallel to the axis and of considerable width. In these are seated the rotary contact members 15 of brass or other convenient material. These may extend the full length of the contact block or be of suflicient length to span two of the adjacent switch blades 3 and 4 or the switch. This switch, as illustrated, is a double pole switch, contact being made when the switch is closed between the two blades I 3 and 4 at the top and the two blades 5 and 6 at the bottom. Obviously either of these two sets of blades may be used alone if desired, giving the elfect of a single pole switch.

The contact block assembly, as illustrated, also includes three insulating disks 16, 17, 18, one being mounted on the hub at each end of the contact block and the other disk 17 'being mounted on the center of the contact block, being seated in a central apperture or notch in the contact member 15. All the disks are coaxial with the contact block. All of these disks are what may be termed battles, the end disks 16 and 18 preventing arcing between the switch blades and the casing or other parts of the switch, as the pawl and ratchet, and the center ,disk 17 preventing arcing between the adj acent blades 3, 4 and 5, 6, particularly at the instant when contact at the switch is broken. The shaft 2 carries nonrotatively secured thereto immediately adj acent the contact member, a ratchet 1'0, having ratchet, teeth 20, as shown particularly in Figure 2, and a square central opening to receive the shaft 2. This ratchet is actuated by means of a pawl 11 having an offset pawl tooth 21. This pawl is mounted on the upper end of trigger 22, which is in turn pivoted at 24 in the casing 25. The trigger has an upwardly extending arm 26, the pawl being pivotally connected at 27 to the upper end of the arm as aforesaid, and extending forwardly into contact with the ratchet 10. The pawl, as shown, has a positioning member 28, which engages a boss 29 on the shaft or on the ratchet.

The pawl is held in contact with the ratchet and the trigger is retracted by means of a spring 31 connected to the pawl arm and to any suitablerelatively stationary member, as the blade block shaft 32. The single spring is found to serve both purposes to advantage.

In the preferred form, as shown, the blades 3, 4, 5, 6 are molded in the blade block 7, the blades 3 and 4 being side by side in the same plane and the blades 5 and 6 being like- Wise side by side in a single plane spaced at their contacting ends from the plane of the blades 3 and 4, preferably by a distance slightly less than the diameter of the contact block 1. In the form shown, the contacting ends of the bladesare turned inward and back at 33 in the form of a U, the v'extreme ends engaging the contact block. The opposite ends ofthe blades seated in the blade block are turned at right angles to the length of the blades at 34 and pierced with suitable holes or eyes to receive the binding screws 35 for the motor wires 36'. Preferably, the blade block is mounted on shaft 32 to rock freely relative to the casing permitting it to adjust itself automaticallyl to the position and contour of the contact block. In case of excessive wear on the contact block or blades this automatic adjustment is of considerable advantage in maintaining uniformity of contact and it further dispenses with the necessity for accurate placing of the block.

The star wheel 8, Figure 3, is mounted on the square portion of the contact shaft 2 the end 38 of which shaft is rounded to form a suitable bearing in the casing, the other end of the shaft carries a head 39 into which it fits and which head engages a bearing 40 in the frame. The star wheel to which reference has just been made serves to give a snapping action of the switch, resulting in a quick making and breaking of the circuit at the points of contact between the blades and the conducting portion of the contact member, eliminating or greatly reducing arcing at these points, particularly at the time of breaking the circuit. The star wheel is engaged by and cooperates with the snapper or snapper arm 9. It comprises a follower or wiper 42 at one end and a bearing 43 at the other' end of the arm, which bearing has a pivotal or swinging engagement with the. blade bl ock shaft 32 and, as shown, the arm 9 is offset intermediately at 44 to span or straddle the points of the star and permit the wiper to contact freely with the star throughout the perlpheral surface of the latter. The snapper mechanism also includes a helical spring 45 connected at one end to a central point on the arm and at the other end to a spring anchor'46, which in the preferred form, as shown, is secured to the trigger shaft 24 which is passed through a suitable eye `or aperture 47 provided in the anchor for this purpose.

In the operation of the switch the points 48 of the star engage the wiper 42 in each instance just prior to 'making and breaking of the contact at the switch. The star wheel turns in left handed rotation in the form of the invention shown and the right hand side of .each point is provided with a sharp incline at 50 so that when the wiper passes the point and ispressed against this sharp incline by the spring 45, a sudden excessive impulse of rotation is imparted to the contact member, the impulse extending over the period of the passage of the wiper down the slope of the star to the point of its working surface nearest the center and this impulse serves to give the snapping action or quick make and 'break referred to. The operation of the'switch, otherwise than as explained, will be easily understood from the preamble, description and drawings. The wiper 42 drops into the depressions 51 on star wheel 48 thereby positioning the contact member in both the on and of positions.

The switch, as described, has the advantages of certainty of operation due to the uniform close contact of the blades with the contact block, long life due to protection against arcing and to the uniform and slight flexing of the blades. vIt is also operated quickly and conveniently by means of the trigger with slight resistance, theparts being immediately returned afterieach make and break to initial position orv breaking operation.

I have thus described specifically and in detail a single switch embodying the features of my invention in, the preferred form in order that the structure of the invention and the method of applying and Operating the same may be clearly understood, however, the specific terms herein are used descripfor the next making tively rather than in a limiting sense, the

scope of the invention being defined in the claims." g lVhat I claim as new by Letters Patent is:

1. An electric switch having a substantially cylindrical contact 'block material with a laterally extending contact member mounted on the surface of the block, contact blades bearing on w and desire to secure said member in one position of the contact block, an insulating baflle projecting radially from the -block and intersecting the contact surface of the contact member between the blades and means for imparting a quick makingiand breaking motion to the contact block 'and positioning the block in on and off position, comprising` a cam member connected to the contact block to rotate therewith and having steeply inclined surfaces corresponding to the making and breaking position of the follower engaging 40 .v the shaft portion of a ratchet and a star Wheel mounted on said projecting portion and positioned 'thereb relatively to the' contact member, a pawl or actuating the ratchet and a follower1 engaging the star the contact block and give a quick change of i contact.

3. In a switch,'a shaft, a tubular hub on the shaft and having a flange at one endand a removable fastener engaging' said hub, a

contact block of insulating material having' a conducting member in Vits surfacel mounted on said tubular hub, a baflle at each end of the contact member also mounted on the hub and held in position by the said flange and said w the surface of the 25 contact block, two of said blades engaging flange andv said fastener, the shaft having a .projecting' wheel member to'position removable fastener and a bafile at the center of the block, the conducting member extending and having contact surfaces on of the center baflie.

Signed by me at Baltimore, Maryland, thls 24th day of March, 1926. 1

' WALTER STUMPF.

of nonconducting surface' mounted both sides Ill 

